Until recently it was thought desirable to reduce or eliminate noise to permit accurate and unambiguous information handling by electronic equipment. Today, however, increased knowledge of electrical noise reveals a structure which can be exploited for useful purposes.
The useful functions of electrical noise derive from its nature which is the result of movement of electric charges associated with electrons. Two aspects are especially significant. First, electrical noise contains frequencies from less than 1 Hz corresponding to the slow drift of electrons in a conductor to higher than microwave frequencies corresponding to the transit time of electron shifts in molecules. It has been found that electrical noise generators provide broad bands of frequencies without resort to many single frequency generators. Second, electrical noise is a useful source of randomly occuring pulses. Since the charges responsible for electrical noise process velocities that vary randomly, the amplitudes of the various electrical pulses also vary randomly. In most noise diode packages to date available, the noise diode is activated by supplying voltage through a current limiting resistor. However, in such packages it has been found that there can be a variance in current over an operating temperature range.
It is therefore a principle object of this invention to prevent current variation by means of a semiconductor device of low noise characteristics for supplying current for the noise diode.
It is a further object of this invention to provide a semiconductor device with a means to variably control current for a noise diode.